A177956 - OEIS

%I #4 Mar 31 2012 14:00:56

%S 2,2,4,60,28,2,234,2,10,186,32,8,22,6,76,330,78,62,462,88,1416,1440,

%T 150,40,308,144,260,42,492,2320,132,328,838,696,736,234,56,2786,172,

%U 382,4872,128,4752,7292,826,1856,3960,1124,424,612,2052,430,1104,280,78,286

%N Smallest k > 0 such that k^prime(n) - prime(n) is prime.

%e 1^prime(1)-prime(1) = 1^2-2 = -1 is not prime, but 2^prime(2)-prime(2) = 2^2-2 = 2 is prime, hence a(1) = 2.

%e k^prime(4)-prime(4) is not prime for k < 60, but 60^prime(4)-prime(4) = 60^7-7 = 2799359999993 is prime, hence a(4) = 60.

%e a(19)^prime(19)-prime(19) = 462^67-67 has 179 digits.

%o (PARI) a177956(n) = {local(k=1, p=prime(n)); while(!isprime(k^p-p), k+=1); k}

%Y Cf. A000040, A084046, A084047, A177832.

%K nonn

%O 1,1

%A Ulrich Krug (leuchtfeuer37(AT)gmx.de), May 16 2010

%E Edited, keywords base, hard removed, PARI program and terms a(21) through a(56) added by the Associate Editors of the OEIS _Klaus Brockhaus_, May 23 2010

%E Extended by _D. S. McNeil_, May 23 2010